As Gerald D. Skoning writes in his enjoyable column, "Just days until Christmas, and I’ve heard enough 'Happy Holidays!' greetings to last a few lifetimes. So, Merry Christmas everyone! Yes, that’s right, Merry Christmas! I’m done with that PC 'Happy Holidays' greeting that has dominated over the past several decades. I haven’t heard a hearty Merry Christmas in years. Why, even Santa has succumbed to the generic mantra, 'HO, HO, HO, Happy Holidays!' Bah, humbug. It’s just not right."
(Actually, since it's less about religion now and more about buying expensive gifts, how about saying Happy Shopmas?)